128 THE DEVELOPMENT OF WEAPONS SYSTEM REQUIREMENTS 

 where pilot requirement = maximum allowable indicated error at firing 

 ^{deH,cldXi)Axi = summation of predictable bias errors 



2^j'E[{^eH,c /dXi)aXiY = twice the standard deviation of the total 

 random error. 



We will assign a value of 2° to the pilot requirement; i.e., the pilot is 

 required only to bring the indicated error within a value of 2° to ensure 

 successful missile launching. This error is, in effect, treated as an allowable 

 predictable bias error and it is desirable that its allowable value be made 

 as large as possible because this will reduce the total time needed to reduce 

 an initial steering error at lock-on (see Fig. 2-49 below). 



For the head-on case, predictable bias errors due to dynamic lags present 

 no problem because the input quantities (R, d, Lm) are relatively constant 

 over the entire attack course and the system is relatively insensitive to 

 mechanization approximations used in the computation of Rq (relative 

 range of the guided missile at impact). Thus, predictable bias errors (other 

 than pilot bias) can be assigned a value of zero for the head-on case. The 

 remaining error tolerance (5°) can be split up among the sources of random 

 error as shown in Table 2-3. It will be noted that no tolerances are given 

 for range and time-to-go quantities; their effect on the head-on attack 

 problem is too insignificant to provide a satisfactory basis for specification. 



The allowable random angular errors (^m, Lm, and pilot steering) are 

 equally divided between the azimuth and elevation channels by dividing 

 the total allowable error by -^2. This analysis shows that the radar must 



Table 2-3 



MEASUREMENT ACCURACY REQUIREMENTS 

 FOR HEAD-ON ATTACKS 



